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  • Users: cherry2000
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  1. cherry2000

    Shield Voltage Calculation for 25kV

    I wanted to know if anybody has carried out calculations for a. Floating voltage b. Circulating current & c.Shield loss per unit length...for 25kV, 3C, cable with core shields ungrounded at one end / grounded at both ends. Interestingly, some relevant sections in IEEE 525-2007 have been removed...
  2. cherry2000

    Picking Data from different Data Sheets

    I have a Data sheet for each LV motor, with various data viz. HP, No of poles, FLA etc. Now, I want to populate a single worksheet with this data against the motor Tag. Is it possible to pick up the data from multiple Data sheets, located in the same folder?
  3. cherry2000

    Reclassification by Ventilation

    I believe this topic has been discussed in the forum previously..Can we reclassify an enclosed area with Ventilation? If we do not want to conduct fugitive emission studies, and we have three air changes (with detectors), is this good enough for a Zone 2 Classification as per API 505?
  4. cherry2000

    Feeding two loads from Single UPS

    I have a query..can we feed two panelboards from a single UPS? Each panelboard has a MLO. The UPS outgoung breaker is 600A rated; each panelboard has 250A bus. Please let me know the relevant sections of NEC, and the options available.
  5. cherry2000

    Generate Data sheets from Template

    I need to generate Data sheets using a Template filled with some generic and some customised information. The customised information is filled in a seperate Database file with a file name. The customised data field is also highlighted in red in the database. Now all the macro needs to do is ...
  6. cherry2000

    VFD-Ground Fault Detection

    We have LV 600V rated VFDs for some of our plant motors. The LV system is resistance grounded. These VFDs do not have any ground fault detection feature. Can anybody give possible options..cheap ones will be appreciated.
  7. cherry2000

    Transformer inrush current - 2

    Once more on the same topic..I could locate some literature for calculating the worst 1st cycle inrush, based on the Transformer parameters like flux density, dimensions etc.See attached. Next, I tried my hand at calculating the reduction in inrush because of line reactance. The reduction was...
  8. cherry2000

    Fusless Current Limiter in Breaker

    Does anybody know how the Current limiter in a breaker works? Typically a breaker has 25kA interrupting capacity which goes upto 100kA with this fuseless current limiter which sits at the load end of the breaker.
  9. cherry2000

    Calculating Transformer Inrush current

    We have a 150kVA Transformer for which we have got the inrush current from the manufacturer. Now we also have 200-400m of cable (cable length differs for each transformer), which should have an effect on the inrush current. Is it possible to calculate the revised inrush current values, if the...
  10. cherry2000

    Tests on MV motor

    We have four 13.8kV, 8000HP motors which were shipped to pump vendors two years back. They have been lying idle since then. These were manufactured as per API 541. The time has come to ship these motors to site. Now the query : What are the tests to be performed to gauge the healthiness of the...
  11. cherry2000

    Generating 12 pulse Rectifier output

    I wanted to simulate a 12 pulse rectifier output in excel and predict the output voltage for variuos firing angles. Does anybody have any idea on this?
  12. cherry2000

    Transformer Primary current

    Consider the Single Phase transformer in the attachment. The rating is 40kVA, and the Primary voltage is 600V. The question : What is the primary line current of this Xmer? Notice that terminals 55 & 56 tied to terminal L2.Also, what shall be the Circuit breaker size for a feeder to this Xmer?
  13. cherry2000

    Cable Ampacity

    We have a General Cable XT-125 Polyriad 1C-250MCM being used for 125VDC application.See attached Catalog. Now, this cable is rated for 95degC termination and ambient of 45degC, and for free air laying. Our conditions are as follows: 75degC termination, 23degC ambient (climate controlled...
  14. cherry2000

    GNB Absolyte IIP Internal Resistance Values

    Bertramh I saw your thread181-27567, requesting the Internal resistances for GNB Absolyte IIP VRLA batteries. The same attached here for your reference.Hope this helps you.
  15. cherry2000

    Motor Contactor Interrupting Rating

    Can anybody tell me the Interrupting rating of Air Break NEMA magnetic Contactor (Size 1 to 5)? Is there any value given by NEMA ICS 2? I wanted this value to check coordination with the upstream MCP in case of fault.
  16. cherry2000

    Contactor Current Breaking rating

    Can any one tell me if NEMA specifies the current breaking rating of NEMA rated magnetic LV contactors? IEC has very specific utilization categories and the Life cycle tests specify both making & breaking currents & power factors. IEEE 242-2001 in Sec 10.4.1.4 says that " NEMA rated magnetic...
  17. cherry2000

    Relay Settings for LV Motors

    In an article in EC&M, "NEMA standards for overload protection need closer look" Jul 1, 1996 12:00 PM, Schindler, Robert, there were some interesting conclusions drawn. Now my question : Is it justified to use a Class 20 relay curve or is the North American industry seriously thinking of...
  18. cherry2000

    Query on Tolerance on Starting Current

    Can someone please tell me the specific Section of NEMA MG-1 which gives the tolerance for starting current for a LV motor?
  19. cherry2000

    Multilin 750 Logic

    We have seperate Transformer Mechanical Alarms being hard wired to Logic Inputs in SR 750 relay (Logic Input 3 through Logic Input 7). See attachment. We want to develop an "OR" logic within SR 750, so that in the event of any of these Mechanical Alarms going high, a common target relay needs to...
  20. cherry2000

    LV Contactor selection for Transformer Switching

    Can somebody help me in selection of LV contactor (starter) for Transformer switching? NEMA ICS 2 Table 2-4-17 gives the max kVA ratings for Transformers with 1 to 20 times of Inrush current. Now for a 600V, single phase application, max. kVA rating is given as 135kVA. However, for us , we have...

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